Effect of YH2 Addition on Microstructure and Mechanical Properties of Zr-Nb Alloy Prepared by Powder Metallurgy

Abstract:

Zr-based alloys prepared by powder metallurgy have the advantages of few macroscopic defects and low cost. However, the high content of oxygen and poor plasticity of this alloy have become the main obstacles restricting its applications. The plasticity of Zr-based alloys prepared by powder metallurgy was improved by doping rare earth hydrides to reduce the O content in alloy matrix. The effects of YH₂ addition content on the microstructure and mechanical properties of Zr-Nb alloys were investigated. The results show that the O content in the matrix is significantly decreased due to the Y₂O₃ formed by doped YH₂ with O in the matrix. On the one hand, more plastic β phase can be retained by the reduction of O content in matrix, which is beneficial to the improvement of plasticity. On the other hand, effects of the dispersion strengthening of Y₂O₃ particles and the grain refinement caused by dislocation pinning by formed Y₂O₃ can both contribute to the improvement of strength. Taking the Zr-Nb alloy added with 2.4wt% YH₂ as an example, the dynamic compressive strength is decreased by 16% and the plasticity is increased by 140% compared with the alloy without YH₂ addition. Decoupling analyses were conducted on the effects of oxygen content, phase composition and grain size on the strength and plasticity of the alloy.